qlalr: add option to error out on warning

By erroring out we can ensure that new warnings are not
accidentally introduced and merged.

As a drive-by: fix indentation of the --qt option. "--dot" needs three
tabs, so "--qt" definitely needs it too.

Fixes: QTBUG-108119
Change-Id: I56107c0744957293338080cf37350f1e1c743093
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Kai Köhne <kai.koehne@qt.io>

src/tools/qlalr/cppgenerator.cpp

@@ -193,7 +193,15 @@ void CppGenerator::operator () ()
     {
       if (shift_reduce_conflict_count != grammar.expected_shift_reduce
           || reduce_reduce_conflict_count != grammar.expected_reduce_reduce)
-        qerr() << "*** Conflicts: " << shift_reduce_conflict_count << " shift/reduce, " << reduce_reduce_conflict_count << " reduce/reduce" << Qt::endl;
+        {
+          qerr() << "*** Conflicts: " << shift_reduce_conflict_count << " shift/reduce, " << reduce_reduce_conflict_count << " reduce/reduce" << Qt::endl;
+          if (warnings_are_errors)
+            {
+              qerr() << "qlalr: error: warning occurred, treating as error due to "
+                        "--exit-on-warn." << Qt::endl;
+              exit(2);
+            }
+        }
 
       if (verbose)
         qout() << Qt::endl << "*** Conflicts: " << shift_reduce_conflict_count << " shift/reduce, " << reduce_reduce_conflict_count << " reduce/reduce" << Qt::endl
@@ -220,7 +228,15 @@ void CppGenerator::operator () ()
       if (! used_rules.testBit (i))
         {
           if (rule != grammar.goal)
-            qerr() << "*** Warning: Rule ``" << *rule << "'' is useless!" << Qt::endl;
+            {
+              qerr() << "*** Warning: Rule ``" << *rule << "'' is useless!" << Qt::endl;
+              if (warnings_are_errors)
+                {
+                  qerr() << "qlalr: error: warning occurred, treating as error due to "
+                            "--exit-on-warn." << Qt::endl;
+                  exit(2);
+                }
+            }
         }
     }
 

src/tools/qlalr/cppgenerator.h

@@ -20,7 +20,8 @@ public:
     aut (aut),
     verbose (verbose),
     debug_info (false),
-    copyright (false) {}
+    copyright (false),
+    warnings_are_errors(false) {}
 
   void operator () ();
 
@@ -29,6 +30,8 @@ public:
 
   void setCopyright (bool t) { copyright = t; }
 
+  void setWarningsAreErrors (bool e) { warnings_are_errors = e; }
+
 private:
   void generateDecl (QTextStream &out);
   void generateImpl (QTextStream &out);
@@ -51,6 +54,7 @@ private:
   int non_terminal_count;
   bool debug_info;
   bool copyright;
+  bool warnings_are_errors;
   Compress compressed_action;
   Compress compressed_goto;
   QList<int> count;

src/tools/qlalr/main.cpp

@@ -28,7 +28,8 @@ static void help_me ()
        << "  --no-debug\t\tno debug information" << Qt::endl
        << "  --no-lines\t\tno #line directives" << Qt::endl
        << "  --dot\t\t\tgenerate a graph" << Qt::endl
-       << "  --qt\t\tadd the Qt copyright header and Qt-specific types and macros" << Qt::endl
+       << "  --qt\t\t\tadd the Qt copyright header and Qt-specific types and macros" << Qt::endl
+       << "  --exit-on-warn\texit with status code 2 on warning" << Qt::endl
        << Qt::endl;
   exit (0);
 }
@@ -42,6 +43,7 @@ int main (int argc, char *argv[])
   bool no_lines = false;
   bool debug_info = true;
   bool qt_copyright = false;
+  bool warnings_are_errors = false;
   QString file_name;
 
   const QStringList args = app.arguments().mid(1);
@@ -64,6 +66,9 @@ int main (int argc, char *argv[])
       else if (arg == "--qt"_L1)
         qt_copyright = true;
 
+      else if (arg == "--exit-on-warn"_L1)
+        warnings_are_errors = true;
+
       else if (file_name.isEmpty ())
         file_name = arg;
 
@@ -104,6 +109,7 @@ int main (int argc, char *argv[])
   CppGenerator gen (p, grammar, aut, generate_report);
   gen.setDebugInfo (debug_info);
   gen.setCopyright (qt_copyright);
+  gen.setWarningsAreErrors (warnings_are_errors);
   gen ();
 
   if (generate_dot)